Lamps used to illuminate moving vehicles have a long history within our technology. The ability to identify the size and type of vehicle is necessary to maintain safety on our roads and highways. The ongoing transition from incandescent light sources to light emitting diode light sources has made such lamps smaller and more power efficient but the limitations set by this new LED technology has not yet been optimized to its fullest extent.
Within the industry of side-marker and clearance lamps there still exists many needs that have yet to be addressed by current technology, chiefly among these needs, is the need to control the light distribution of the LEDs in directions most beneficial to the use of such lamps. Most side-marker and clearance lights to date, direct the majority of their light, generally outward or perpendicular to the side of the base of the lamp. This fact points up the inefficiency of such lights as a vehicle is, even without illumination, most visible when viewed from a perpendicular angle. The need in the industry is to make vehicles more visible when viewing them from an angle to these lamps. Therefore there is a need within the industry for side-marker and clearance lamp that directs more light at a longitudinal angle to the lamp's base.
The first method attempted to meet the need included having the light sources mounted high off the base of the lamp or angled at a slope in relation to the base, but the problems of having a high profile are obvious. Susceptibility to damage, increased drag and vibration made these solutions unacceptable in the market
Other technology such as that claimed in U.S. Pat. No. 6,623,150 “Light-emitting diode combination marker/clearance lamp for trucks and trailers” by Roller, et al. has attempted this redirection of light through the use of reflecting or refracting elements integrated into outer lens of the lamp. These have proven effective but introduce several problems such as a high profile prominence and non-streamlined outer surface of the exterior of the lamp that causes increased drag, resonant harmonic noise and vibrations as well as collection points for road dirt and debris that reduce the overall light output. Similar lamps using exterior Fresnel, lenticular, or generally obstructed outer topographies are subject to collections of road dirt to a degree of near total opacity.
Another solution attempted is the use of reflective surfaces partially encasing the LEDs within the lamp to channel the light in the desired direction as is demonstrated in U.S. Pat. No. 6,095,663 “Combination clearance and marker light assembly” by Pond, et al. These too have proven effective but introduce certain problems. The first of which is difficulty in manufacturing, in that fitting metal or plastic reflective chambers around each LED is a non-automated task requiring significant amounts of time and can reduce manufacturing yields and efficiency. The second is over heating due to the lack of heat distribution which is inhibited by the isolation of the reflective surfaces. Increased heat is known to reduced LED's lifespan and therefore the operational duration of any such lamp.
Therefore what is needed is an LED generated light source lamp for use as a side-marker or clearance light that can direct a significant percentage of its light at an angle to the lamp and has the advantages of having a low profile, a streamlined outer lens, and no restrictive or thermally isolative encasement of the light source, which includes an uncomplicated method of manufacturing.